Piston



March 7,1939. A 'CORTHALS' 2,149,423

PISTON Filed March ll, 1936 mg g 4 //J////V /I/ w NVENTDR:

Patented Mar. 7, 1939 PISTON Auguste Corthal s, !miles-Brussels, Belgium Application March 11, 1936, Serial No. 68,249

In Belgium March 13, 1935 Claim. 4. (CI. sos-11 The present invention relates to a piston for internal combustion engines, explosion motors and other like engines in which the heat absorbed by the piston and the cylinder produces y a relatively 'considerable expansion of these elements.

It is known that the provision of the piston pin bosses produces an unequal distribution of the heat in the skirt of the piston and consequently o causes unequal expansions of the latter from one point to another in one and the same circular section.

For the purpose of eliminating this drawback, it has been proposed to use a yelding piston,

- ll which aifords a more considerable capacity of deformation in determined directions. This piston presents the drawback, owing to its lack of rigidity, to become detormed in an excessive and unadmissible mannerat the moment when it produces the driving eifort upon the connecting rod. The deformations produced in this manner cause an important friction of the piston in the corresponding cylinder.

It has also been proposed to use semi-rigid pistons, by means of which the drawbacks of the yielding pistons were reduced. These pistons present, in a reduced manner, the drawback of the rigid pistons consisting in a lack-of capacity to follow the deformations of the cylinders. This latter drawback also remains with unsymmetrical rigid pistons, which present the advantage of'securing a better distribution of heat.

With these different types of pistons, it is moreover necessary to provide supplementary play according to determined diameters.

Finally, it has been proposed to make the skirt yielding and to make it integral with the head, independently of the piston pin bosses which were rigidiy connected to the head by strong webs, independent of the skirt and attached to the head towards the middle portion thereof.

In the pistons of this type, the skirt is separated from the pin bosses by a groove which encircles entirely or partially these bosses.

By the fact that the central portion `of the head has a higher temperature than the edges,

' said bosses become more heated than ii they were integral with the head by means of the skirt. Moreover, they cannot eliminate the complete 0 portion of the heat they contain by conduction towards the skirt, because they are completely or partially separated from the latter. It results thereirom that their temperature is much higher than in the other known pistons. By this u fact, the difference between their expansion and that of the piston pin is greater and a play is produced between these elements when the motor becomes heated. The repeated knockings which are produced in these conditions between these elements cause, aiter a. certain delay, the rupture of the pin bosses. The pistons oi this latter type also present the drawbak of necessitating different chili moulds for each spaclng between the pin bosses.

p The present invention has for its object to reio tan the advantages resulting from the use of a. yielding skirt independent of the said bearings, while not presenting the drawbacks of the last mentioned type of pistons.

For this purpose, the yielding skirt is construct- !5 ed so as to be also deformable in the direction of all its diameters.

The invention will be described hereaiter with reference to the accompanying drawing.

Fig. 1 is a perspective view, partially broken. 20

of the embodiment of a piston according to the invention having four longitudinal slots;

Flg. 2 is a partia] longitudinal section of this piston at right angles to the axis of the piston pin bosses; 5

Flg. 3 is a transverse section through the skirt .of a piston having eight longitudlnal slots;

Fig. 4 is a longitudinal section through the piston of Fig. 2, passing through the axis of the pin bosses.

In these figures, the same reference characters designate identical elements.

The 'piston illustrated in Figs. 1 to 4 comprises a head 2, to which are rigidly connected the piston pin bosses 3. by means of webs 4, said bosses 35 being also united to that part of the skirt in which are provided the grooves |3 for lodging the piston rings.

Except for the head side, the bosses 3 are separatedfrom the skirt 5 by a. slot E cutting com- 40 pletely the thickness of the skirt.

The piston skirt according to the invention is so constructed that it can also be deformed in the direction of all its diameters. It is formed with four parts sa, Sb, Sd, si, yieldingly united to each other by inner yielding ribs 1. These ribs are arrangedcapproximately at the angles of a square 8, shown in dotted lines in Flg. 1. Two sides of this square are almost parallel to the axis of the bosses 3.

The parts Sa, 5b, Ed, 5f, which have thus almost the same width, are separated from each other by slots 9, III, ll and I2. These slots are cut in the ribs T according to planes which are not radlal planes'. Two oi these planes, tor instance the planes of the slots 9 and I I are directed almost parallel to the side sa, paraiiel to theaxis of the bosses 3. The two other planes, those of the slots o and !2, are directed almost parallel to the side ob, at right angles to the axis of the bosses 3.

As lt may be seen' on examination of Flg. 1, the

slots arranged atthe diametrically opposed angies of the square are directed paraliel to the same side thereof.

The depth of the slots 9 to |2 is such that, assuming that the inner ribs 'I extend almost over the length of the parts 5a`, 5b. id, 5! and are of the same composition as the Iatter, the remaining thickness of these ribs at the bottom of the slots be less than the thickness of said parts. In this way, the ribs 'I are more yielding than the parts mentioned. Ribs presenting such yield combined with the provision of slots in planes dfierent from the radial planes constitute an important characteristic of the invention. Owing to' this, the skirt is made perfectiy yielding in all directions and fits Conveniently the shape of the cylinder containing the skirt.

The slots 9, [0, H and 12 could be directed par- .allel to the generating lines of the cylindrical surface of the skirt, but they are preferably directed in a known manner somewhat obliquely with relation to these generating lines, so as to scrape the oil covering the inner surface of the cylinder.

, It is to be noticed that for producing a peri'ectly yielding skirt, it is required that the parte mentioned be at least four in number.

In Fig. 3 has been illustrated a transverse section through the skirt of a piston which is furthermore divided by a set of four supplementary 5 slots ll, IE, IS, l'l of similar arrangement to that of the slots 9, o, l l and |2 but oifset with respect i to this first set at an angle of substantially This skirt thus comprises eight parts -almost of the same width. -1 Whatever may be the form of embodiment used, the inner yielding ribs, which are known per se, may be continuous or interrupted and formed from the same material as that which constitutes the parts they connect, or from a.. material different from that of these parts. Use could namely be made, in the case of a skirt in aluminium, of inneryieiding ribs of Invar or steel.

I claim: I 2

ly tangent to a circle concentrically located in- 30 side the piston' skirt.

AUGUSTE CORTHALS. 

